Mountains and freeways, oceans and apartment buildings, trees and automobiles: such things lend shape to mental activity, says Christopher J. Preston. Yet Western epistemology, since its origins, has neglected these material factors. Even postmodern perspectives on how we think and know continue to emphasize social and cultural factors over the physical environment.Grounding Knowledge claims that one of the unforeseen consequences of this anthropocentrism has been to ignore the epistemic argument for maintaining diverse natural environments. Grounding Knowledge supplies that argument. Preston first traces the separation of place and mind in Western epistemology. Drawing connections between skepticism and ungrounded knowledge, he then explores how a common insight in the epistemologies of both Kant and Quine sets the scene for more situated accounts of knowledge. After showing how science studies and cognitive science have both recently moved in this direction, Preston draws further evidence for his thesis from fields as far apart as evolutionary biology, anthropology, and religious studies. He asks what these ideas in contemporary epistemology and environmental philosophy mean for environmental policy, concluding that the grounding of knowledge strongly suggests epistemic reasons for the protection of a full range of physical environments in their natural condition.Grounding Knowledge comes at a time of increasing dialogue between the sciences and the humanities about our rootedness in all of our different worlds. Preston hopes to persuade his readers that it is not only in our biological but also in our cognitive interests to protect these roots.